Track fallback formats to use in the memoryformat directly instead of
using in the GL uploading code.
First of all, this allows sharing the code and ensuring all our
renderers use the same fallback mechanism.
But also, this allows tracking fallbacks per-format which is useful
because the fallback formats aren't really a tree. We want to make
FLOAT16 fall back to FLOAT32 when not available, but we also want
FLOAT32 fall back to FLOAT16.
By tracking the fallbacks per-format, we can achieve that.
Add gdk_memory_format_get_premultiplied() and
gdk_memory_format_get_straight() which return the matching
premultiplied/straight format.
Use this to pick the premultiplied format when uploading GL textures.
And remove the duplication in the dmabuf code, where we can now use
these functions instead of tracking both the premultiplied and straight
alpha versions.
Add an "RGBA" format that just maps to the swizzled version of the
default format.
This way, BGR gets mapped to RGB + swizzling first before trying to map
it to the default format for the depth.
The benefit here is that this format has the same memory width, so
uploading/downloading code can treat it equivalent to the original
format and there's no conversion neccessary later.
Now that we have gdk_gl_context_get_memory_flags() and code can use that
function, make the code do that.
Remove support checks from gdk_memory_format_gl_format().
This is an initial naive port that doesn't try to make use of the finer-grained
flags yet.
Make gdk_memory_format_gl_format take the GdkGLContext,
instead of just a gles boolean. This will let us
check for extensions that may be needed for certain
formats.
Update all callers.
Replace gdk_memory_format_prefers_high_depth with the more generic
gdk_memory_format_get_depth() that returns the depth of the individual
channels.
Also make the GL renderer use that to pick the generic F16 format
instead of immediately going for F32 when uploading textures.
Make it use gdk_memory_texture_from_texture().
Also make gdk_memory_format_alpha() privately available so that we can
detect if an image contains an alpha channel.
Also, now make gdk_memory_convert() the only conversion functions
and allow conversions between any 2 formats by going via a float[4].
This could be optimized via fast-paths, but so far it isn't.
